The research, conducted by Jeff Pettis of the US Department of Agriculture, shows that bees are taking the unusual step of sealing off cells containing pollen with wax in what looks like an attempt to keep contaminants away from the hive population. (Bees do not usually seal off cells containing pollen.) Unfortunately, however, Harvey reports that the evidence shows such efforts largely resulting in failure:

"This is a novel finding, and very striking. The implication is that the bees are sensing [pesticides] and actually sealing it off. They are recognising that something is wrong with the pollen and encapsulating it," said Jeff Pettis, an entomologist with the US Department of Agriculture. "Bees would not normally seal off pollen."

But the bees' last-ditch efforts to save themselves appear to be unsuccessful - the entombing behaviour is found in many hives that subsequently die off, according to Pettis. "The presence of entombing is the biggest single predictor of colony loss. It's a defence mechanism that has failed." These colonies were likely to already be in trouble, and their death could be attributed to a mix of factors in addition to pesticides, he added.